1. Field of the Invention
The present invention relates to a leaktight fitting for a shaft end, particularly for a shaft end located in a housing and protected from the outside by a cap that can be removed when required.
2. Discussion of the Background
The advantages of this type of shaft end may be understood by studying FIG. 1 which shows a gas turbine. Working from front to back along an annular gas circulation channel 1, are fitted a blower 2, a low pressure compressor 3, a high pressure compressor 4, a combustion chamber 5, a high pressure turbine 6 and a low pressure turbine 7. The channel 1 contains fixed, circular blade stages constructed as part of a housing 8 that delimits the outside of the channel and rotating blades connected to a rotor 9 that delimit the inside of the channel. The rotor 9 also comprises a line of low pressure shafts 10 that interconnect the blower 2, the low pressure compressor 3 and the low pressure turbine 7, as well as a line of high pressure shafts 11 that interconnect the high pressure compressor 4 and the high pressure turbine 6. The lines of shafts 10 and 11 are coaxial and the line of high pressure shafts 11 surrounds the line of low pressure shafts 10. The line of shafts ends at the front in a conical gear wheel that co-ordinates with a first conical gear wheel of a transmission shaft 12 radially positioned to form an angled gear 13. Another angled gear 14 is formed at the opposite end of transmission shaft 12 between another conical gear wheel mounted on the shaft and a final conical gear wheel located at the rear end of shaft end 15. Shaft end 15 lies parallel to the shaft lines 10 and 11 and next to the low pressure compressor 3 and the blower 2. Its forward end finishes behind a plane surface 16 of housing 8, opposite an aperture 17 that is closed by a cap 18 gripped by an elastic ring 19 clamped between the cap and aperture 17. This ring 19 also ensures the leaktightness of aperture 17.
The shaft end 15 allows individual inspection of the blades connected to the line of high pressure shafts 11 and particularly the blades of the high pressure compressor 4. It is known that blades are relatively fragile structures that can be easily damaged, for example when a foreign body is introduced into the gas turbine. The method for inspecting the blades consists firstly in disassembling the gas turbine and opening a window of housing 8 facing one of the stages of the rotating blades to be inspected, usually the first of compressor 4, and then rotating the line of high pressure shafts 11 in order that all the blades of the stage pass successively in front of the window. Movement is brought about using a key (not shown, but of standard design) which is inserted into an opening located at the front of shaft end 15. The key is inserted through slot 17 once the cap 18 is removed and can be operated by hand or by a dedicated device. A drawback, however, of this construction is that the operator may forget to replace cap 18, resulting in a large quantity of the oil contained in housing 8 draining from aperture 17 as soon as operation of the gas turbine is resumed, thus rapidly emptying the housing 8. Despite seal 19, cap 18 may also be accidentally dropped.